1. Field of the Invention
The present invention relates to a hub and, more particularly, to a rear hub for a bicycle.
2. Description of the Related Art
A conventional rear hub for a bicycle in accordance with the prior art shown in FIGS. 9-11 comprises a shaft 40, a hub body 10 rotatably mounted on the shaft 40 by a plurality of bearings 41 and provided with two protruding spoke mounting portions 11, a mounting ring 13 mounted on a first side of the hub body 10 and located beside one of the two spoke mounting portions 11, a driven member 12 mounted on a second side of the hub body 10 to drive and rotate the hub body 10 and located beside the other one of the two spoke mounting portions 11, a brake disc 30 mounted on the mounting ring 13 of the hub body 10, and a drive member 20 rotatably mounted on the shaft 40 and engaged with the driven member 12 to drive and rotate the driven member 12.
The shaft 40 has two opposite ends each provided with a threaded portion 42 for screwing a locking nut 43. Each of the two spoke mounting portions 11 of the hub body 10 has a periphery provided with a plurality of fixing holes 110 for fixing a plurality of spokes (not shown) of a rear wheel (not shown). The brake disc 30 is used for clamping a brake (not shown) to produce a speed reduction function. The mounting ring 13 of the hub body 10 has a periphery provided with a plurality of screw bores 14, the brake disc 30 is provided with a plurality of through holes 31, and the hub further comprises a plurality of locking screws 15 each extending through a respective one of the through holes 31 of the brake disc 30 and each screwed into a respective one of the screw bores 14 of the mounting ring 13. The driven member 12 has an inner wall provided with a plurality of oneway ratchet teeth 120. The drive member 20 has a first end provided with a oneway ratchet wheel 21 meshing with the oneway ratchet teeth 120 of the driven member 12 and a second end provided with a freewheel 22. Thus, the drive member 20 is rotatable to drive and rotate the driven member 12 in a oneway direction by engagement between the oneway ratchet wheel 21 and the oneway ratchet teeth 120 of the driven member 12 so as to drive and rotate the hub body 10 in a oneway direction.
As shown in FIG. 11, when the shaft 40 is mounted on a rear frame 45 of the bicycle, the locking nut 43 is rotated on the respective threaded portion 42 of the shaft 40 to press the rear frame 45 onto the hub body 10 so as to attach the hub body 10 to the rear frame 45.
In assembly, the hub body 10 is connected to a rear wheel (not shown) of the bicycle, the shaft 40 is connected to the rear frame 45 of the bicycle, the freewheel 22 of the drive member 20 is driven by a chain (not shown) which is driven by a chainwheel (not shown) which is driven by a pedal (not shown) that is pedalled by a rider.
In operation, when the freewheel 22 of the drive member 20 is rotated, the drive member 20 is rotatable to drive and rotate the driven member 12 in a oneway direction by engagement between the oneway ratchet wheel 21 of the drive member 20 and the oneway ratchet teeth 120 of the driven member 12 to drive and rotate the hub body 10 in a oneway direction so as to drive and rotate the rear wheel in a oneway direction.
Thus, when the bicycle is used in an acrobatic place, the rear wheel is often inclined to be very close to the ground for performance of acrobatics. However, the drive member 20 and the brake disc 30 are located at the two opposite sides of the hub body 10 and have a projecting shape so that when the rear wheel is inclined to have a determined inclined angle, the drive member 20 or the brake disc 30 easily contacts raised equipments in the acrobatic place or even rubs the ground, thereby interfering with movement of the bicycle, and thereby easily wearing the drive member 20 or the brake disc 30.